Waterproof acoustic element enclosures and apparatus including the same

ABSTRACT

A waterproof enclosure for a cochlear implant system or other hearing assistance device includes an outer housing, an inner support in the interior of the outer housing, an acoustic element supported by the inner support, and water-impermeable polymeric protective membrane sealing the interior of the outer housing against water ingress. A hearing device such as a cochlear implant sound processor, a headpiece, an earhook, or a hearing aid comprises an outer housing, an inner support in the interior of the outer housing, a microphone supported by the inner support, and a water-impermeable polymeric protective membrane sealing the interior of the outer housing against water ingress. A method for waterproofing an acoustic element comprises molding an outer support having a water-impermeable polymeric protective membrane; inserting an acoustic element into an inner support; anchoring the acoustic element to the inner support; inserting the inner support into the outer support; and anchoring the inner support to the outer support.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of 13/635,399, filed Sep. 14, 2012,which is the U.S. National Stage of PCT app. Ser. No. PCT/US2011/028905,filed Mar. 17, 2011, claims the benefit of U.S. Provisional ApplicationSer. No. 61/315,826, filed Mar. 19, 2010 and entitled “WaterproofMicrophone Enclosure,” each of which is incorporated herein byreference.

BACKGROUND

1. Field

The present inventions relate generally to waterproof enclosures foracoustic elements such as microphones and speakers, and may be describedin the context of microphones used with a sound processor of a cochlearimplant system; however, it should be understood that the inventionshave application in other apparatus that include acoustic elements, suchas microphones and speakers, and are exposed to moisture.

2. Description of the Related Art

Many acoustic devices are inherently sensitive to moisture and areeasily damaged by water. Any apparatus that requires a microphone,speaker or other acoustic device, and needs to be water resistant orwaterproof, must address this weakness. In the exemplary context soundprocessors and microphones, commercially-available microphones thatoffer protection from water are generally either too large or sufferfrom poor performance under the conditions that patients would like touse their sound processors. Waterproof microphones implementing sealedacoustic chambers are large and complex, and may have an undesirablefrequency response, making them impractical for use with cochlearimplants. Water-repellent membranes that prevent liquid water ingressbut allow vapor-phase transport and have minimal impact on sound qualitymay be sufficient for splash-protection, but they cannot provideprotection in water immersion or long-term protection from water vapor.Other problems inherent in previous designs include holes, recesses, andcavities that fill up with water and take a long time to dry. Previousdesigns using silicone barriers are subject to the problem that siliconeabsorbs water and releases it very slowly, and also that silicone tendsto dampen the sound. A microphone can be sealed by dipping it in apolymer, but these designs are not feasible in a small form factormicrophone, and typically suffer from poor acoustic performance.

SUMMARY

The present inventions provide acoustic element (e.g., a microphone orspeaker) water protection that affords similar acoustic performance asnon-waterproof acoustic elements and long-term immersion protection fromliquid and vapor-phase water, and do not suffer from the shortcomings ofthe prior solutions. To provide an acoustic element that performs wellin harsh environments, we have developed novel enclosures to make theacoustic element waterproof, using a thin film membrane material toprotect the acoustic element. The present inventions also provide amethod of assembling the enclosure to minimize performance variations.The membrane may be integrated with the microphone housing, and thehousing may include a vent.

The present inventions solve the problems that plague current waterproofing techniques for microphones and other acoustic elements. Theyimplement a chamber that contains the acoustic element, which iscompletely sealed from the surrounding environment by a thin, durable,water-impermeable, polymeric protective membrane. The membrane'smechanical and physical characteristics are selected to optimizeacoustic element performance in the frequency spectrum of interest forhearing devices, such as cochlear implants, hearing aids, and the like,while affording the microphone complete protection from long-termimmersion and vapor-phase moisture. The mechanical structure is suchthat a user can clean the membrane periodically to remove anyaccumulated debris without damaging the membrane.

The inventions are also easily cleanable, and therefore can be kept freeof cerumen (ear wax) and other debris that could potentially damage orcompromise the performance of other sound pickup devices. This sealedacoustic element eliminates failures due to debris and otherenvironmental factors, allowing patients to use their systems withoutworrying about environmental impact on their devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinventions will be more apparent from the following more particulardescription thereof, presented in conjunction with the followingdrawings wherein:

FIG. 1 is a view of a cochlear implant system in accordance with oneembodiment of a present invention;

FIG. 2A is a view of a behind the ear sound processor in accordance withone embodiment of a present invention;

FIG. 2B is a view of a body worn sound processor in accordance with oneembodiment of a present invention;

FIG. 3 is a cross-sectional view of a microphone assembly in accordancewith one embodiment of a present invention;

FIG. 4 is a top view of the microphone enclosure of FIG. 3 without theprotective membrane;

FIG. 5 is a cross-sectional side view of a microphone assembly inaccordance with one embodiment of a present invention;

FIG. 6 is a cross-sectional side view of a microphone assembly inaccordance with one embodiment of a present invention;

FIG. 7A is a block diagram of a hearing aid in accordance with oneembodiment of a present invention;

FIG. 7B is a cross-sectional view of a speaker assembly in accordancewith one embodiment of a present invention;

FIG. 8 shows the typical frequency response of a sound processormicrophone, with and without a protective membrane, respectively; and

FIG. 9 shows an exemplary production process for the production of awaterproof enclosure.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description of the presently contemplated best modes ofpracticing the inventions is not to be taken in a limiting sense, but ismade merely for the purpose of describing the general principles of theinventions. The scope of the inventions should be determined withreference to the claims. It should also be noted that although thepresent inventions are discussed below primarily in the context ofmicrophones and cochlear implant systems, they are not so limited. Byway of example, but not limitation, the present inventions haveapplication in the context of speakers and other acoustic elements aswell as in hearing aids (e.g. in-ear hearing aids) and other auditoryapparatus.

One example of an acoustic element that may require protection frommoisture is a microphone, and a cochlear implant system is one exampleof an auditory apparatus that may include a microphone and also includeor embody at least some of the present inventions. To that end, FIG. 1illustrates a cochlear implant system 1000 comprising internalcomponents 200 and external components 100. The internal components 200comprise an antenna coil 210 and implanted electronics 220, and a lead230 having an electrode array implanted within the cochlea. The externalcomponents 100 include a headpiece 110 and sound processor 140.

FIGS. 2A and 2B illustrate external components, 100 and 100′,respectively, having behind-the-ear and body-worn sound processors, 140and 140′, respectively and batteries, 120 and 120′, respectively. Theseprocessors have various controls such as sensitivity controls, volumecontrols, and programs switches, and may include various additionalfeatures such as a built-in LED status indicator 160 and an auxiliaryport 170. A waterproof enclosure 10 may be used to protect a microphonein any number of locations within the cochlear implant system 1000,including the headpiece 110 (as shown in FIG. 2B), the behind-the-earprocessor 140 or body-worn sound processor 140′, or an earhook 130(e.g., a T-mic® in-the-ear microphone).

FIG. 3 is a cross-sectional view of a first embodiment of a waterproofenclosure, which is generally represented by reference numeral 10,comprising a water-impermeable, polymeric protective membrane 20 mountedon an outer housing 30. The membrane 20 is shown in an unstressed state.The waterproof enclosure 10 includes an inner support 40, which supportsa microphone 70 to define a waterproof microphone assembly. As shown inFIG. 3, inner support 40 may be integral with outer housing 30;alternatively, the inner support 40 may be formed by a separatecomponent mounted within outer housing 30, as shown and described withrespect to FIGS. 5 and 6.

FIG. 4 is a top view of the waterproof enclosure without protectivemembrane 20, showing microphone 70 mounted within inner support 40. Tocomplete manufacturing of the waterproof enclosure 10 (FIG. 3),protective membrane 20 would be bonded or welded to the top surface 36of outer housing 30, such as by pressure sensitive adhesive orultrasonic welding. Alternatively or additionally, the protectivemembrane 20 may be smoothed over the top of the outer housing 30 andextend down the sides of the outer housing 30 and captured by a metallicor hard plastic hoop, which may be tightened like a drumhead. Additionaladhesive may be used to bond the side walls of the outer housing 30 tothe extended protective membrane 20. In some embodiments, the adhesiveused is not elastic and/or is kept thin to avoid sound dampening. Forexample, a pressure sensitive adhesive may be used to join the membrane20 to the housing 30, applying high forces to compress it; the jointthus formed may then be sealed with epoxy. As another alternative, themembrane 20 may comprise a material that can be thermally bonded to athermoplastic or metal housing. The housing material is chosen toprovide good adhesion by whichever attachment mechanism is used. Asanother alternative, a molded plastic outer housing 30 may be formedintegral with thin protective membrane 20, as shown and described withrespect to FIGS. 5 and 6.

FIG. 5 is a cross-sectional view of another embodiment of a waterproofenclosure, which is generally represented by reference numeral 10 a.Waterproof enclosure 10 a is similar to enclosure 10 and similarelements are represented by similar reference numerals. Here, however,the inner support 40 a comprises a separate support component mountedwithin an outer housing 30 a. The outer housing 30 a may be generallycylindrical, having a curved side wall 31 that is integral with a flatend face. The flat end face forms a protective membrane 20 a, which isshown in an unstressed state. The flat end face (i.e., protectivemembrane 20 a) is very thin compared to the curved side wall 31. Thisstructure may be micromolded out of a polymer such as polypropylene,polyethylene terephthalate, or other material with suitable propertiesfor the application and processing. The outer housing 30 a has anexterior vent 32 formed therein that vents to atmosphere to enable thepressure to equilibrate inside and outside the microphone cavity. Arecess 34 formed in the outer housing 30 a provides space for aprotective cover such as a mesh (not shown) that prevents particulatematerial from entering the vent system. A microphone 70 is mountedwithin inner support 40 a within outer housing 30 a to form a waterproofmicrophone assembly. The inner support 40 a has a circumferential groove50 and a narrow channel 51 to allow airflow through the vent 32. Theback of the assembly may be potted (not shown) to prevent water ingress.

FIG. 6 illustrates another alternative embodiment of a waterproofenclosure, which is generally represented by reference numeral 10 b andis similar to the embodiment illustrated in FIG. 5 but without theexternal vent system in the outer housing. Here too, the exemplaryenclosure 10 b has a molded plastic outer housing 30 a that is formedintegral with the thin protective membrane 20 a, which is shown in anunstressed state. The inner support 40 b captures the microphone 70,thereby defining a waterproof microphone assembly, and is shaped toprevent damagingly large displacements of the protective membrane causedby users pressing or rubbing the protective membrane 20 a.

Another acoustic element that may require protection from moisture is aspeaker and one example of an auditory apparatus that may include aspeaker and include or embody at least some of the present inventions isan in-ear hearing aid. Turning to FIGS. 7A and 7B, the exemplary in-earhearing aid 100″ includes a microphone assembly with a microphone 70 ina waterproof enclosure 10, a battery 120″, sound circuitry 140″, and aspeaker assembly with a speaker 71 in another waterproof enclosure 10.In other embodiments, the enclosures 10 a and 10 b may be employed inconjunction with the microphone 70 and/or speaker 71.

The protective membrane 20 (or 20 a) protects the acoustic elementagainst moisture but is itself exposed to the environment. Therefore,shape, structure, and materials of the enclosures 10-10 b are selectedsuch that they can be cleaned regularly without damage to the protectivemembrane, as is discussed in greater detail below. Because theprotective membrane is exposed without a screen over it, it can beeasily cleaned using a soft brush or damp towel, and there is nooverlying mesh to get clogged.

The exemplary protective membrane 20 (or 20 a) is thin, tough, flexible,and water-impermeable, and may be made out of a polymer such as liquidcrystal polymer (LCP), polyester, such as polyethylene terephthalate(PET) (e.g., Mylar® PET film), polyimide (e.g., Kapton® polyimide film),or polypropylene. The polymer is chosen to be strong, punctureresistant, and thermally, chemically, and mechanically stable. The filmmaterial is also chosen to sufficiently inhibit the transport of waterthrough the membrane such that the microphone, speaker or other acousticelement behind the membrane is not damaged. The exterior of a polymericprotective membrane 20 (or 20 a) may be plasma treated and coated with ametallic or nonmetallic material, such as titanium dioxide, to preventtransport of water through the membrane. The coating may also preventdamage from ultraviolet (UV) radiation, make the assembly moreaesthetically pleasing, and provide a substrate for a hydrophobiccoating.

The membrane 20 (or 20 a) is as thin as possible, such as less than 5mil (0.005 inches, 0.18 mm) thick Mylar® PET film or nylon or less than5 mil (0.005 inches, 0.18 mm) thick Kapton® polyimide film. Whether theprotective membrane is integral with the outer housing (e.g., membrane20 a) or a separate component (e.g., membrane 20), the protectivemembrane may be thinned in a secondary process, such as by laserablation, selective dissolution, or mechanical thinning, to enhance thesensitivity of the microphone, speaker or other acoustic element insidethe waterproof enclosure 10 (or 10 a or 10 b).

A cavity 60 is formed by the inner support 40 (or 40 a) and protectivemembrane 20 (or 20 a) and may have a geometry chosen to minimizeundesirable acoustic effects, e.g., resonance. The diameter of theprotective membrane 20 (or 20 a) is large enough to ensure sufficientmicrophone sensitivity, while the cavity 60 has a small enough volume tosuppress cavity acoustic effects (e.g., attenuation). In someembodiments, the ratio of protective membrane diameter to acousticelement membrane diameter may be 1.5 or more. The diameter of theacoustic element membrane (membrane 72 in FIG. 5) may be approximated asbeing equal to the diameter of the acoustic element itself. The surface41 (or 41 a) of support member 40 is concave, and may be conical,parabolic, or otherwise tapered to become narrower towards the interiorof the outer housing 30. The shape of the support member surface 41 (or41 a) is designed to have no sharp transitions in the portion formingthe wall of the cavity 60 and no sharp transition between the supportmember and the microphone 70, speaker 71 or other acoustic element,thereby minimizing unwanted reflections.

The protective membrane 20 (or 20 a) will deflect when pressed during,for example, cleaning of the protective membrane. Various attributes ofthe protective membrane 20 (or 20 a) and the support member 40 (or 40 aor 40 b) are selected so as to prevent failure of the protectivemembrane. The shape of the surface 41 (or 41 a or 41 b) of the supportmember that faces the membrane, for example, is designed to have nostress concentration so as to avoid damage to the protective membrane 20(or 20 a). For example, the shape of the surface may be the same as thebending profile of the protective membrane under a uniform load. Themembrane material, shape and dimensions, as well as the dimensions ofthe cavity 60, are selected such that when external pressure is appliedto the membrane during cleaning or use, the membrane will stretch butnot permanently deform or tear. The membrane 20 (or 20 a) contacts thesupport member surface 41 (or 41 a) and the microphone 70, speaker 71 orother acoustic element, which act as a stop, prior to the membranematerial reaching its elastic limit (or yield stress). In other words,the distance between the protective membrane and the acoustic elementmust be less than the deflection distance that will result in permanentdeformation or tearing of the protective membrane.

The shape, thickness and modulus of the protective membrane, as well asthe distance between the protective membrane and the acoustic element,are such that stress on the protective membrane will be less than theyield stress when the protective membrane is pressed into contact withthe acoustic element. Put another way, the distance between membrane andthe acoustic element defines the maximum distance Y_(max) that themembrane can be deflected from its at rest state (note FIG. 3). DistanceY_(max) is less than the deflection distance at which a membrane of aparticular shape, thickness and modulus would reach its elastic limit inthe absence of the stop provided by the support member surface andacoustic element.

In those instances where the protective membrane is disc-shaped, thedeflection distance Y_(c) that will result in the membrane materialreaching its elastic limit may be calculated using the followingequations:

${D\; 1} = \frac{E \times t^{3}}{12 \times \left( {1 - v^{2}} \right)}$and$Y_{c} = {\frac{q \times r^{4}}{64 \times D\; 1} \times \frac{\left( {5 + v} \right)}{\left( {1 + v} \right)}}$

where

E=modulus of the membrane material,

t=membrane material thickness,

v=Poisson's ratio,

q=load/area=uniformly distributed load, and

r=membrane radius (portion that is free to deflect).

Accordingly, Y_(c) may be calculated for a given enclosure to determinewhether or not Y_(max)<Y_(c), as is demonstrated by the followingnumerical example. If the protective membrane in an acoustic elementassembly is a PET film that has a modulus of 2×10⁹ Pa, a thickness of0.127 mm and a radius of 3.175 mm, that v=0.35, and that the loadimparted by a finger during cleaning is 0.5 N (i.e., 63.2 KPa for the3.175 mm radius), then Y_(c)=1 mm. The predicted stress under theseconditions is 49.5 MPa, which is on the order of the yield stress.However, because the deflection of the membrane is constrained by thesize of the cavity under the membrane, the maximum stress will bereduced relative to the free condition and the stress in the membranewill be significantly less than the yield stress. Thus, so long asY_(max) is less than 1 mm, it may be assumed that the maximum membranedeflection permitted by the assembly will be less than that which wouldresult in failure. Y_(max) may be further reduced, as compared to Y_(c),by an appropriate safety factor (e.g. 20%).

In some embodiments, and depending on the protective membrane materialtype and thickness, the ratio of Y_(max) to membrane diameter will beless than 0.25, or less than 0.10, or less than 0.05, or less than0.025.

In view of the above-described issues associated with acoustics andprotective membrane preservation, the portion of the membrane that iscoextensive with the cavity 60 and free to deflect in some embodimentscan be, for example 0.125 to 0.300 inches (3.18 mm to 7.62 mm) indiameter, or 0.180 to 0.260 inches (4.57 mm to 6.60 mm) in diameter, or0.250 to 0.260 (6.35 mm to 6.60 mm) inches in diameter. The distancebetween the protective membrane and the top of the microphone, speakeror other acoustic element can be less than 0.05 inches (1.27 mm), or onthe order of 0.005 to 0.010 inches (0.13 mm to 0.25 mm), or less.

The waterproof enclosure may be combined with a variety of otherwaterproofing technologies to provide further waterproofing for themicrophone, speaker or other acoustic element.

FIG. 8 shows a frequency response of a device with and without theprotective membrane 20 of the present invention. Typically, it isdesirable that the microphone remain sensitive over a broad range ofhearing frequencies, such as 100 to 8500 Hz or even 100 to 10,000 Hz. Inthe example shown in FIG. 8, adding the protective membrane reducedsensitivity by less than 10 dB over the frequency range of 100 to 10,000Hz. In this example, the housing was made of a rapid prototypingmaterial, E shell pink photo-reactive acrylic, and the membrane wasapproximately 0.001 inch thick Mylar® PET film.

FIG. 9 illustrates a method 800 for making the waterproof enclosurehaving separately-molded inner and outer supports, 40 a and 30 a,respectively, such as shown in FIG. 5 or 6. The method is described inthe context of a microphone, but is also applicable to speakers andother acoustice elements. In step 810, the outer support having awater-impermeable polymeric protective membrane is molded. The outersupport may be molded onto a prefabricated film, or the film may beformed at the same time as the structural support during the moldingprocess. In step 820, the microphone is inserted into an inner support.In step 830, the microphone is anchored to the inner support, such as bypress fitting, adhesively bonding, or potting. This anchoring stepserves to consistently define the distance between the microphone 70 andthe membrane 20 (FIG. 5). This may be done by using capture featuresthat ensure correct microphone position and orientation. In step 840,the inner support is inserted into the outer support. In step 850, theinner support is anchored to the outer support, such as by an adhesivebond.

While the invention herein disclosed has been described by means ofspecific embodiments and applications thereof, numerous modificationsand variations could be made thereto by those skilled in the art withoutdeparting from the scope of the invention set forth in the claims.

1-28. (canceled)
 29. In a hearing assistance device selected from thegroup consisting of a cochlear implant sound processor, a headpiece, anearhook, and a hearing aid, the improvement comprising: an acousticelement assembly including an outer housing defining an interior, aninner support in the interior of the outer housing, an acoustic elementsupported by the inner support, and a water-impermeable polymericprotective membrane that seals the interior of the outer housing againstwater ingress and is spaced a predetermined distance from the acousticelement when in an unstressed state, the protective membrane defining ashape, a thickness, a modulus and a yield stress, wherein there is apredetermined relationship between the shape, thickness and modulus ofthe protective membrane and the predetermined distance between theprotective membrane in its unstressed state and the acoustic element,and wherein, as a result of the predetermined relationship, stress onthe protective membrane will be less than the yield stress when theprotective membrane is pressed from the unstressed state into contactwith the acoustic element.
 30. A hearing assistance device as claimed inclaim 29, wherein the acoustic element comprises a microphone.
 31. Ahearing assistance device as claimed in claim 29, wherein the acousticelement comprises a speaker.
 32. A hearing assistance device as claimedin claim 29, wherein the inner support and outer housing are anintegrally formed unit.
 33. A hearing assistance device as claimed inclaim 29, wherein the inner support and the outer housing are separatestructural elements.
 34. A hearing assistance device as claimed in claim29, wherein the inner support has a tapered surface that faces theprotective membrane.
 35. A hearing assistance device as claimed in claim29, wherein the protective membrane is formed from a material selectedfrom the group consisting of liquid crystal polymer, polyethyleneterephthalate, polyester, polyimide, polypropylene and polyamide.
 36. Ahearing assistance device as claimed in claim 29, wherein the protectivemembrane and the outer housing are an integrally formed unit.
 37. Ahearing assistance device as claimed in claim 29, wherein the protectivemembrane and the outer housing are separate structural elements and theprotective membrane is mounted on a surface of the outer housing.
 38. Ahearing assistance device as claimed in claim 37, wherein the protectivemembrane is joined to the surface of the outer housing using aninelastic adhesive to form a joint.
 39. A hearing assistance device asclaimed in claim 38, wherein the inelastic adhesive comprises a pressuresensitive adhesive.
 40. A hearing assistance device as claimed in claim38, wherein the joint is sealed with epoxy.
 41. A hearing assistancedevice as claimed in claim 29, further comprising a circumferential ventbetween the outer housing and the inner support.
 42. A hearingassistance device as claimed in claim 41, further comprising an exteriorvent formed within the outer housing in communication with thecircumferential vent.
 43. A hearing assistance device as claimed inclaim 29, wherein the protective membrane is not covered by a meshstructure.
 44. A hearing assistance device as claimed in claim 29,wherein the protective membrane is disc-shaped.
 45. A hearing assistancedevice as claimed in claim 44, wherein the protective membrane defines adiameter; the acoustic element includes a membrane defining a diameter;and the ratio of protective membrane diameter to acoustic elementmembrane diameter is 1.5 or more.
 46. A hearing assistance device asclaimed in claim 45, wherein the ratio of predetermined distance toprotective membrane diameter is 0.25 or less.
 47. A hearing assistancedevice as claimed in claim 46, wherein the protective membrane has adiameter of 0.125 to 0.300 inches (3.18 mm to 7.62 mm), and the distancebetween the microphone and the protective membrane is less than 0.050inches (0.127 mm).
 48. A hearing assistance device as claimed in claim44, wherein the predetermined distance is less than the deflectiondistance Y_(c) that will result in the protective membrane reaching itselastic limit, as calculated by the following equations:${D\; 1} = \frac{E \times t^{3}}{12 \times \left( {1 - v^{2}} \right)}$and$Y_{c} = {\frac{q \times r^{4}}{64 \times D\; 1} \times \frac{\left( {5 + v} \right)}{\left( {1 + v} \right)}}$where E=modulus of the protective membrane material, t=protectivemembrane material thickness, v=Poisson's ratio, q=uniformly distributedload, and r=protective membrane radius.